Description (Adapted from Application): The overall objective of this proposal is to examine the hypothesis that expression of eicosanoid compounds in algae is related to stress conditions. The relationship is hypothesized to be based on eicosanoid action as an intracellular signal. Eicosanoids are biologically active molecules that are involved in many basic human metabolic functions, playing important roles in mammalian homeostasis where they are present in virtually every mammalian tissue and body fluid and where they exert a broad spectrum of physiological activities. Establishment that eicosanoids evolved as stress management compounds, and that their role has been conserved through evolution would provide a functional homology with one of its major roles in animals, where the lipoxygenase-mediated formation of leukotrienes and lipoxins serves as a signal to initiate stress responses within the organisms. The objectives will be carried out by culturing the target species, Murrayella periclados, and examining the time courses of lipoxygenase enzyme induction, eicosanoid expression, and subsequent stress protein expression. Stress protein identification will employ two-dimensional SDS PAGE. Eicosanoid concentrations will be measured using ELISA assays. A molecular probe for Murrayella lipoxygenase will be developed and the resultant gene or gene fragment will be utilized to produce polyclonal antibodies. The antibodies will then be used to follow lipoxygenase induction following stress conditions utilizing ELISA assays. That eicosanoids act as a signal will be tested with Murrayella that has been cultured to be deficient in lipoxygenase products.